Now to convert bits to bytes...
How many bits in a byte? (8 is normal, but i think in modern computing it is 10 bits (maybe 11, can't remember) in a byte if you include the trailing and initial bit. something like [info][01010101][trailing bit])

Either way:
2595840/10 = 259584 bytes
or
2595840/8 = 324480 bytes

Then divide the number of bytes by your cluster size (512bytes) and you should get either:
a)507 clusters (for a byte of 10bits)
b) 633.75 clusters (for a byte of 8bits)

Seeing that the clusters should be round numbers, I would round off answer b) to 634 clusters. What do you think?

Since the old times, the number of sectors per track was constant. I just updated myself and found out that using ZBR (zone bit recording), the bit density remains more or less optimal throughout the disk by assigning different number of sectors/cylinder to different zones. The following link presents a detailed description of the techniques, and hence a better understanding of what information that is required to do the calculation.

Also, rotational latency refers to the delay required by the arm to switch from one track to the adjacent one. For the 7200 RPM drive, the time for one complete rotation is 60/7200=8.33 ms.
The company claimes a SUSTAINED speed of 78 MB/s, equivalent to 624 Mbit/sec for an 8-bit byte. So the sustained read time per track is 8.33 ms - 4.16 ms = 4.17 ms.
The rest of the calculations are essentially the same as Redargon had done, since 4.17 ms is almost identical to 4.16 ms used in the calculations. However, if the rotational latency had not been exactly half of the rotational time, the results could be different.

ok, you're on the right track. just one calc error:
1500/60=25 rotations per second, not 250.
then it would be 1.128/25=0.04512Gbit per rotation.
0.04512Gbit= 45.12Mbit= 5.64MB (assuming 8bits per byte)= 5.64x10^6 Bytes (per rotation that can be read)
so, then 5.64x10^6/512 = 11015.625 sectors, so around 11016 sectors

oh, and I think your formula looks ok too. (just remember to keep your units consistent) If you use t, rotation time in seconds, then you will get an answer in bytes/s with that formula, as you are multiplying by 512, which is bytes per sector